Silicon based packages are known to have significant potential affect upon packaging technology. As explained in Development of Next-Generation System-On-Package (SOP) technology Based on Silicon Carriers with Fine-Pitch Chip Interconnection, Knickerbocker et al., IBM J. Res. & Dev. Vol. 49, No. 4/5 July/September 2005, which is hereby incorporated by reference, some useful features of silicon based packages include: dense wiring using back-end-of-line (BEOL) processing; increased chip package interface reliability; the use of interconnections like advanced solder microbumps or permanent copper interconnections; the ability to embed active devices into the carrier itself; and for carriers having through-vias the support of heterogeneous semiconductor technologies, passive or active circuits and high-density I/O wiring interconnections with electro-optic technology, as well as the support of three-dimensional circuit integration.
The full potential of silicon carriers cannot be fully realized, however, until problems related to thermal mismatches between various components of silicon based packages are overcome. Broadly speaking, a silicon based package is comprised of various components including, chips, carriers having various bumps and underfills, and substrates, all of which may be made of the same or different materials and have different thermal and mechanical stresses placed upon them. For a more in-depth discussion of silicon based packages, any of several sources may be relied upon, including G. W. Doerre and D. E. Lackey, “The IBM ASIC/SoC Methodology—A Recipe for First-Time Success,” IBM J. Res. & Dev. 46, 649 (2002), and D. J. Bodendorf, K. T. Olson, J. P. Trinko, and J. R. Winnard, “Active Silicon Chip Carrier,” IBM Tech. Disclosure Bull. 7, 656 (1972).
For example, the useable size of a chip can be limited by the thermal mismatch between a silicon chip and substrate. If a chip is too large, the stresses at the largest distances from the thermal neutral point on the underfill, solder balls, and chip can exceed the material strengths and cause failures and/or material fatigue, and/or package warpage such that the useable limits for attachment or cooling solutions are exceeded. There is a similar issue with silicon carriers where multiple chips are attached to a silicon carrier interposer which is added between the chips and package or circuit board. A silicon carrier can be made thinner to increase its flexibility; however, this limits the robustness of the carrier relative to the forces placed on it during bonding and thermal cycling due to the bumps above and below the carrier which exert loads on the carrier.
A need has therefore been recognized in connection with providing an effective means for reducing the thermo-mechanical stresses created by thermal mismatches between chip, carrier, and substrate.